Mass spectrometry, electrospray ionization sample preparation

Wetzel, S.J., Guttman, C.M. and Flynn, K.M., The influence of electrospray deposition in matrix-assisted laser desorption/ionization mass spectrometry sample preparation for synthetic polymers. Rapid Commun Mass Spectrom, 18 (2004) 1139-1146. 

Fion, N., Gellon, J. O., Jensen, H., and Girault, H. H. (2003). On-chip protein sample desalting and preparation for direct coupling with electrospray ionization mass spectrometry. ]. Chromatogr. A 1003, 11-19. 

A sensitive and rapid chromatographic procedure using a selective analytical detection method (electrospray ionization-mass spectrometry in SIM mode) in combination with a simple and efficient sample preparation step was presented for the determination of zaleplon in human plasma. The separation of the analyte, IS, and possible endogenous compounds are accomplished on a Phenomenex Lima 5-/rm C8(2) column (250 mm x 4.6 mm i.d.) with methanol-water (75 25, v/v) as the mobile phase. To optimize the mass detection of zaleplon, several parameters such as ionization mode, fragmentor voltage, m/z ratios of ions monitored, type of organic modifier, and eluent additive in the mobile phase are discussed. Each analysis takes less than 6 min. The calibration curve of zaleplon in the range of 0.1-60.0 ng/ml in plasma is linear with a correlation coefficient of >0.9992, and the detection limit (S/N = 3) is 0.1 ng/ml. The within- and between-day variations (RSD) in the zaleplon plasma analysis are less than 2.4% (n = 15) and 4.7% (n = 15), respectively. The application of this method is demonstrated for the analysis of zeleplon plasma samples [14]. 

Because anurans, including L. splendida, often breed in water, the peptide components of the secretions of the paratoid and rostral glands were purified directly by HPLC. The active component was sequenced with the aid of electrospray ionization mass spectrometry (ESI-MS) and given the name splendipherin (17).76 The structure of this 25-amino acid peptide subsequently was confirmed by comparison with a synthetically prepared sample, which further established that all amino acids were of the L-configuration. 

As a rule, a separation method should be used for both purification and concentration of the sample. The classic method for peptides and proteins is a reverse-phase liquid chromatography preparation of the sample, followed by a concentration step (often lyophiliza-tion) of the fraction of interest. During those steps performed on very small quantities of sample, loss on the sample can occur if care is not taken to avoid it. Lyophilization, for instance, can lead to the loss of the sample absorbed on the walls of the vial. The use of separation methods on-line with the mass spectrometer often are preferred. Micro- or nano-HPLC [32,33] and capillary electrophoresis [34], both coupled mainly to electrospray ionization/mass spectrometry (ESI-MS), are used more and more. 

Analyses of tropane alkaloids are mainly carried out by GC and HPLC and to a lesser extent by CE. This review describes recent applications developed for the analysis of this class of compounds in plant materials and biological matrices. Of course, mass spectrometry is generally used as the detection technique because of its high sensitivity and selectivity, but other techniques such as UV, fluorescence, flame ionization detection, nuclear magnetic resonance, among others have also been investigated. Finally, desorption electrospray ionization mass spectrometry is reported as a new interesting detection technique for the rapid analysis of samples without any sample preparation. 

Abdel-Rehim, M. Hassan, Z. Skansen, P. Hassan, M. Simultaneous determination of busulphan in plasma samples by liquid chromatography-electrospray ionization mass spectrometry utilizing microextraction in packed syringe (MEPS) as on-line sample preparation method. J. Liq. Chromatogr. Relat. Technol. 2007, 30, 3029-3041. 

Laser-induced acoustic desorption-electrospray ionization mass spectrometry (LlAD-ESl/MS) is a technique combining an electrospray and a pulsed laser beam to characterize solid and liquid samples with minimal sample preparation [48]. Although the instrumental setup of LIAD-ESl is similar to that of ELDl, the laser intensity required for LIAD (i.e., 10 W/cm ) is higher than that for ELDl, and the desorption mechanism of LIAD is also different from that of LD. In LIAD, the sample is not desorbed by direct laser irradiation, but by acoustic and shock waves induced by the laser irradiation. A pulsed laser beam with a flux energy of several mJ is used to irradiate the rear of a thin metal foil (e.g., AL Ti, Cu, and Ta 5-25 pm thickness) to generate acoustic and shock waves [48-50]. These laser-induced... 

Chen H, Pan Z, Talaty N, Raftery D, Cooks RG (2006) Combining desorption electrospray ionization mass spectrometry and nuclear magnetic resonance for differential metabolomics without sample preparation. Rapid Commun Mass Spectrom 20 1577-1584... 

Apffel A, Chakel JA, Fischer S, Lichtenwalter K, Hancock WS. Analysis of ohgonucle-otides by HPLC-electrospray ionization mass spectrometry. Anal Chem. 1997 69 1320-5. Sauer S. The essence of DNA sample preparation for MALDl mass spectrometry. J Biochem Biophys Methods. 2007 70 311-8. 

Several mass spectrometric techniques including fast atom bombardment (FAB), plasma desorption (PD), matrix-assisted laser desorption/ionization (MALDI), and electrospray (ES) mass spectrometry (MS) are presently available for the analysis of peptides and proteins (Roepstorff and Richter, 1992). Of these techniques, mainly PDMS has gained footing in protein laboratories because the instrumentation is relatively cheap and simple to operate and because, taking advantage of a nitrocellulose matrix, it is compatible with most procedures in protein chemistry (Cotter, 1988 Roepstorff, 1989). Provided that the proper care is taken in the sample preparation procedure most peptides and small proteins (up to 10 kDa) are on a routine basis amenable to analysis by PDMS. Molecular mass information can be obtained with an accuracy of 0.1% or better. Structural information can be gained by application of successive biochemical or chemical procedures to the sample. 

Mass spectrometry (MS) is widely used to ascertain the purity, total mass of the protein produced, and detect any covalent modifications (Cohen and Chait, 2001). Both electrospray ionization (ESI) and MALDI may be used although for intact proteins ESI has the advantage of being accurate to 1 Da. Using the simple protocol described in Protocol 2.11, the MS of whole protein samples can be readily automated without the need for sample preparation. This method has proved successful for the... 

A newer approach for lipid analysis is electrospray ionization tandem mass spectrometry (ESI-MS/MS) (Welti et al., 2002). This method requires limited sample preparation and sample size to identify and quantify lipids. Fauconnier et al. (2003) used ESI-MS/MS to analyze phospholipid and galactolipid levels during aging of potato tubers. 

Detection techniques of high sensitivity, selectivity, and ease of coupling with sample preparation procedures are of special interest for measuring PGM content in biological and environmental samples. ICP MS, electrothermal atomic absorption spectrometry (ET AAS), adsorptive voltammetry (AV), and neutron activation analysis (NAA) have fotmd the widest applications, both for direct determination of the total metal content in the examined samples and for coupling with instrumental separation techniques. Mass spectrometry coupled with techniques such as electrospray ionization (ESI) and capillary electrophoresis (CE) (e.g., ESI MS", LC ESI MS", LC ICP MS, CE MS", and CE ICP MS) offer powerful potential for speciation analysis of metals. MS is widely used for examination of the distribution of the metals in various materials (elemental analysis) and for elucidation of the... 

---